1. Field of the Invention
The present invention relates to a technology for remotely controlling a vehicle based on a communication between a portable device held by a passenger and an on-board terminal installed in a vehicle.
2. Description of the Related Art
In recent years, an in-vehicle system has been proposed in which doors of a vehicle are locked and unlocked through communication with a portable device. This system is referred to as a keyless entry system or a smart entry system. In some keyless entry systems, in addition to a configuration in which locking and unlocking are performed when a user (a passenger outside of the vehicle) operates the portable device, a configuration in which locking and unlocking are performed automatically depending on a distance between the portable device and the on-board terminal is also provided.
Reduction of power consumption of the portable device is an important issue. A keyless entry system disclosed in Japanese Laid-open Patent Publication No. 2000-145223, for example, determines a distance between the portable device and the on-board terminal from positional information of the portable device and positional information of the on-board terminal and changes the power consumption of the portable device depending on the distance.
Furthermore, a smart entry system disclosed in Japanese Laid-open Patent Publication No. 2001-40921 lengthens transmission period of a response request from the on-board terminal to a portable device depending on the amount of time a driver is in a transmission and reception coverage area of the vehicle when exiting the vehicle.
In the conventional technologies, first, an on-board terminal transmits a query signal to a portable device, and the portable device returns back a response signal only upon receiving the query signal. Inductive communication having a short range, which requires less stand-by power consumption, is used for communication from the on-board terminal to the portable device and radio communication having a long range is used for communication from the portable device to the on-board terminal thereby reducing overall power consumption.
However, because the inductive communication is limited to a narrow range, the on-board terminal can communicate with the portable device only when the portable device is in the range. In addition, the door is locked when the portable device moves out of the inductive communication range (i.e., when there is no response from the portable device), and thus, the on-board terminal cannot provide information to the portable device thereafter.
However, when the vehicle is parked in a wide area such as a parking area of a store, for example, preparations for boarding are preferably made in advance by detection of the passenger from a relatively far distance. On the other hand, when the vehicle is parked in the narrow area such as a home garage, the portable device may enter the inductive communication range and the door may be unintentionally unlocked because the user, who can be the driver or the possessor of the vehicle, or just a passenger, passes near the vehicle for reasons other than to board the vehicle.
In addition, the portable device cannot be notified that the door has been locked because the door is locked when the portable device moves out of the inductive communication range, and thus, the user cannot confirm that the door has been locked.
In other words, the state of the vehicle is unknown at the portable device side, and therefore, the portable device cannot give notifications to the user autonomously.
For example, if the user holding the portable device moves away from the vehicle while the engine is running or when the door lock is unlocked and the engine is stopped or the door is locked thereafter, other users cannot restart the vehicle because they does not have the portable device. Conventionally, the vehicle gives out a warning by sounding a horn, etc., to prevent such situations from occurring. However, the user does not always take notice of the warning, and furthermore, the warning becomes a nuisance if the user is intentionally moving away from the vehicle while the engine is running. Regardless of there being situations as such, in which warnings are preferably given by the portable device, these situations were not taken into consideration in the conventional technologies.
In other words, in the conventional technologies, the operations of the portable device and the on-board terminal are fixed. Thus, there is need of a technology that performs appropriate operation according to the situation cannot be performed.